In such energy generating stations, for example nuclear power stations having a pressurized-water nuclear reactor, quantitative or qualitative information relating to the operation or state of the various components of the power station is gathered continuously. This information, generally called "parameters", is compared with reference data corresponding to normal operation of the power station and, in the event of a significant difference between a parameter and a reference datum, gives rise to a signal or an alarm in the control room of the power station.
These signals or alarms must be taken into account by an operator who must, if appropriate, intervene to prevent a dangerous development in the state of the power station or the occurrence of a malfunction or an accident making it necessary to take appropriate action.
However, such a monitoring system makes the operator's job relatively complex under certain circumstances.
Thus, when a malfunction or an accident occurs in the power station, the operator is faced with a very large number of alarms which it is difficult to act upon in a very short time. This happens, for example, after an emergency shutdown or after a phase of safety injection. It is then very difficult for the operator to distinguish the fault which led to the malfunction causing the emergency shutdown and/or the safety injection.
It has therefore been proposed to adopt a monitoring system in which it was possible by successive interrogations to arrive at the cause of the malfunction by itemizing all the relations of cause and effect between the events occurring in the power station.
Such a process leads to the use of very large memories and complex logics. The time required for the successive interrogations also risks preventing an effective and rapid intervention by the operator. Moreover, it is never possible to be certain of having thought of all the possibilities.